Use of a computerized postural sway measurement system for neurobehavioral toxicology.

A computerized postural sway measurement system for use with neurobehavioral toxicology studies was described. The system consisted of a six component high frequency response force platform equipped with temperature compensating foil type strain gauge transducers, a signal conditioner and amplifier, and a microcomputer. The force platform was sunk into the floor and bolted to a baseplate that was anchored in concrete to minimized effects of building vibrations. The microcomputer software provided analog to digital data printouts from all six recording channels in the platform. Changes in neurobehavioral performance were detected by measuring the sway parameters: horizontal position of the subject, mean center of position pressure relative to the center of the platform, length of sway path, area included within the sway path, mean radius of sway, standard deviation of center of pressure about the mean y-position, and mean velocity along the sway path. The system was relatively free of practice and motivation effects. No consistent statistically significant sex differences were seen in any of the sway parameters. Height and weight were significantly correlated with mean center/of/position pressure, length of sway, sway area, and mean velocity along the sway path. Statistical power calculations showed that for 90% power at least 40 subjects per cell were needed for a two group study and 26 for a four group study. The authors conclude that postural sway analysis techniques are feasible for use with neurobehavioral toxicity testing.